The use of adhesives to bond two elements, the adhesive being applied to one or both of the contacting surfaces of the elements is, of course, well known. Where time is relatively unimportant, the surfaces are simply pressed together for a suitable duration until the adhesive has cured at which point there will exist a generally satisfactory bond between the surfaces.
Where the time required for bonding takes on significance, however, as in modern packaging and manufacturing operations, the time required for the known bonding process becomes of importance and various techniques have been utilized to decrease the time required for bonding. One such technique is known as the "hot melt" procedure. In this procedure, adhesive which is solid at ambient temperature is heated to a much higher temperature hich liquifies the adhesive. The adhesive is then applied to one or both of the surfaces and the surfaces are held in contact while the adhesive temperature decreases and it again solidifies. This procedure, however, is unsafe due to the high temperature required for the adhesive to liquify and is costly because of the necessity for high heat and an adhesive with the required characteristics.
Another known technique is that disclosed in U.S. Pat. No. 1,851,709 entitled METHOD OF HOT GLUING to Laucks et al. This technique requires one piece of lumber or board to be heated to a temperature relatively higher than the other piece of similar material and, thereafter, joining the heated element with the unheated element by applying pressure between the two pieces. This technique taught by Laucks et al, however, does not contemplate the high speeds required by modern packaging requirements and, in any event, it does not relate to corrugated paper elements which have distinctly different properties relating to pressure and temperature characteristics.
Yet a further known method utilizes adhesive of the water based variety which can be utilized at ambient temperatures. In this technique, high mechanical pressure and small adhesive droplets dispersed over the area to be bonded are utilized. Where fragile contents are used in, for example, the boxes which are desired to be closed, high mechanical pressure cannot be used for fear of damage to the contents. The time required for suitable bonding using this method, however, remains relatively high which is unacceptable.